The invention relates to a device for vaporizing liquid fuel prior to its introduction into the combustion chambers of an internal combustion engine or a gas turbine, to an internal combustion engine or a gas turbine which contains such a device and to automotive vehicles which contain such an engine or gas turbine.
The conventional spark-ignition gasoline engine relies on a carburetor to mix a desired proportion of a volatile fuel with the inlet air. For complete combustion of the fuel-air mixture the fuel needs to be uniformly dispersed in the air. Such a uniform mixture is seldom if ever obtained in practice with a conventional carburetor, and manifold fuel injection offers only marginal improvement. In the conventional gas turbine a uniform fuel-air mixture is equally hard to achieve.
It has been proposed to vaporize the fuel prior to its introduction into a combustion chamber and prior to or after mixing it with the main stream of combustion air, with heat derived from the exhaust system, this heat being transported with the aid of a heat transfer fluid present in one or more so-called heat pipes, each of which is in the form of a substantially sealed vessel containing a heat transfer fluid having a boiling point at atmospheric pressure up to 400.degree.C and so constructed that in operation the heat transfer fluid in the said heat pipe or heat pipes is evaporated in the so-called heat receiving zone of the heat pipe by heat received from the exhaust gases of the said engine, and condensation of the said evaporated heat transfer fluid taking place by discharging heat for the evaporation of fuel to be combusted in the so-called fuel vaporizing zone of the heat pipe.
The use of vaporized fuel enables a gasoline engine to be run on such lean mixtures, even in excess of 20:1 air-fuel ratio, that the levels of carbon monoxide and oxides of nitrogen are simultaneously low, thereby contributing to the abatement of environmental pollution.
The amount of heat transfer fluid that should be present in the heat pipe is related to the amount of fuel to be evaporated during running of the engine and it must in all cases even at high load and high speed, be sufficient to be able to transport the required amount of heat to evaporate the fuel from the heat receiving zone of the heat pipe to the fuel vaporizing zone of the heat pipe.
At cold start no hot exhaust gases are available and consequently no heat can be obtained therefrom for evaporation of the fuel. It has been proposed to use additional heating means at the start which heat and evaporate heat transport fluid in the heat pipe and thus provide heat which can be discharged to the fuel for the evaporation thereof. The additional heating means may e.g., consist of an electrical heating coil or a self-blowing gasoline blow lamp.
It is felt as a drawback that the total amount of heat transport fluid present in the heat pipe is to be heated to or nearly to its boiling temperature at cold start with the additional heating means discussed because this heating is evergy-consuming, and in particular time-consuming.
The time between the moment one wants to start driving an automotive vehicle and the moment the fuel can be evaporated is of importance, because evaporation of the fuel ensures running of the engine without the formation of undesirable amounts of noxious compounds such as carbon monoxide and nitrogen oxides in the exhaust gases, as described above.
There has now been found a device which makes evaporation of the amount of fuel required at cold start less time- and less energy-consuming.